ORAL ANTI-CANCER AGENTS: BRIDGING THE final.pdf¢ ORAL ANTI-CANCER AGENTS:...
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ORAL ANTI-CANCER AGENTS:
“BRIDGING THE GAP”
Aimed to Provide Pharmacists with Necessary Tools to Care for the Cancer Patients
To provide community pharmacists with the necessary tools for provision of pharmaceutical care to cancer patients, as it relates to drug distribution and patient education.
To raise awareness about the supportive resources available to community pharmacists in the oncology field.
To discuss the role that the community pharmacist plays in a cancer patient’s care. To provide practical advice regarding the specifics of caring for cancer patients. To identify the red flags in a patient’s condition, which require referral.
BASIC ONCOLOGY PRINCIPLES: Cancer refers to any uncontrolled growth of malignant cells, which if left undetected can destroy the organs and their functions. Currently there are more than 200 distinct forms of cancers known and this number keeps on growing. Despite the fact that many cancers are more prevalent in the elderly, no age group is immune to this disease. Although cancer originates in our own cells, there are both intrinsic and extrinsic factors that can increase one’s risk of developing cancer. The intrinsic factors include the age, hormonal status and genetic predisposition (family history). The extrinsic factors consist of the following: diet, lifestyle, smoking and alcohol use, exposure to toxic chemicals, radiations and even some infections. Asbestos, dyes, food additives, vehicular emission and many other chemicals are carcinogenic and increase the risk of cancer development, especially if an individual concurrently has positive intrinsic factors. Once the malignant tumor has developed it will be progressing and eventually it may metastasize (i.e. spread to other organs and tissues in the body). This process depends on the metastatic changes that lead to invasion of local normal tissues, entry of the neoplastic cells into the blood and lymphatic systems and the resultant development of secondary tumors at distant sites.
PRESCRIPTION FOR ANTI-CANCER AGENT: Why is this important to you?
Despite the fact that these patients are taken care of by specialists with expertise at CancerCare
Manitoba (CCMB): The doctors know that you will be involved in the patient’s care and rely on you for that final
check No matter how specialized and expert in the area one is – every human has the potential of
making errors. Being overly reliant on someone’s expertise opens more gaps in the system! Critical incidents
From the recent critical incidents it is evident that there are serious gaps in the system that guides the care of patients who are taking oral anti-cancer agents.
1. A patient with neutropenia was given a handwritten prescription for cyclosporine. Due to the “sound-alike” drug name and poor handwriting the patient had received cyclophosphamide instead of cyclosporine. After taking 8 doses the patient realized that a mistake was made and presented to the emergency department, from where he was discharged and started on the correct medication.
2. A patient was prescribed capecitabine 2000 mg BID for 14 days. It was discovered later that based on the patient’s creatinine clearance a dose reduction was indicated. The pharmacy where the prescription was taken was phoned and a dose reduction to 1500 mg BID was ordered. However, the patient received and took capecitabine 2000 mg.
3. A patient was prescribed tretinoin 40 mg (ATRA – all-trans retinoic acid was indicated on the prescription). The prescription was filled for cis- retinoic acid (i.e.: isotretinoin or Accutane).
These critical incidents demonstrate the necessity to improve the care “bridge” between CCMB and community pharmacies. The survey about oral anti-cancer agents that was sent out in November – December of 2011, revealed that of the pharmacists who responded, only 11-16% feel comfortable dispensing and counseling on oral anti-cancer agents. Therefore, providing pharmacists with relevant tools to increase their comfort level in dispensing and counseling on these medications is of key importance.
SPECIFIC STEPS IN ANTI-CANCER AGENT PRESCRIPTION APPROACH:
1. Verify patient’s information
Although this step is critical in filling any prescription, the anti-cancer agents have a very narrow therapeutic window and it is important to appreciate the significance and the great extent of complications if a patient is misidentified.
In addition to the patient’s full name, need at least 1 specific identifier out of these 2: PHIN DOB
Note: address is not considered a specific identifier
2. Confirm the appropriateness of the treatment
If diagnosis, indication or protocol is indicated on the prescription, or if you know the diagnosis from the patient, then you can check the appropriateness using the sources we will be talking about further (BCCA website).
You can check the eligibility and contraindications based on the information you know, and if any concerns or doubts arise – do not hesitate to call the clinic!
Specific link: http://www.bccancer.bc.ca/HPI/default.htm Cancer management guidelines Chemotherapy protocols
Important note re. eligibility: MB criteria for use may be different than in BC
Intent of treatment is very important in treatment rationale and the protocols are categorized according to the one of the four intents of treatment:
Neo-adjuvant – chemotherapy given before the surgical procedure in an attempt to shrink the cancer in order to have less extensive surgery.
Adjuvant – chemotherapy aimed to destroy the left-over cancer cells after the visible tumor has been removed by surgery. The goal is the prevention of cancer reoccurrence.
Induction – chemotherapy aimed to induce a remission (commonly used term in treatment of leukemias)
Consolidation – chemotherapy given to sustain a remission once it has been achieved. Maintenance – chemotherapy given to assist in prolonging the remission (usually lower
doses are used). Palliative – chemotherapy given to address particular cancer symptoms to improve the
patient’s quality of life, without targeting or expecting to reduce the cancer.
Confirm that the dosing regimen matches the indication and the intent of treatment. This can be easily done once you access the protocol. Appendix 1 contains a table demonstrating the common indications and dosing regimens for most common oral anti-cancer agents.
Once you have identified the appropriate dosing regimen - check that the dose was calculated
correctly. Anti-cancer agents may be dosed based on BSA (body surface area, mg/ m²), weight (mg/kg) or sometimes the doses are fixed based on the indication.
BSA can be calculated using a number of formulas, and unfortunately, just like with creatinine clearance the results may vary depending on the formula used. Therefore, it is important that during checking process same formula that was used to calculate the dose is used, in order to avoid unnecessary confusion.
Currently CCMB uses the Mosteller formula, which is presented below:
BSA (m²) = √ [(Height(cm) x Weight(kg))/ 3600]
e.g. BSA = √ [(cm*kg)/3600]
Once you know the BSA, you can divide the prescribed dose by BSA to ensure its accurateness according to the recommended dosing regimen.
Often you may see that the dose used is not exactly the one recommended by the regimen, but close to it. This is done by the system to ensure that there is no need to split the tablets and the rounding is usually done based on the drug monograph recommendations.
It is important to note that even though the BSA might be provided, it is best if the pharmacist calculates it based on the patient’s height and weight and using the formula provided above. That will eliminate the possibility of a computer-related error (e.g. data entry error). For the same reason, try to always confirm the height and weight with the patient first.
As it has been discussed above, kidney function is very important and often serves as the guide
for dosing. Thus, creatinine clearance (Clcr) is a very important piece of information to be considered when checking the dose.
Therefore, if the serum creatinine / Clcr is provided you should take that into account when checking the appropriateness of the treatment.
Just like with the BSA, it is best to re-calculate the creatinine clearance based on the serum creatinine (if provided). Currently CCMB uses the Cockroft-Gault formula for calculating estimated Clcr:
Clcr = [(140 – age) x weight] / (sCr x 1.2*) *1.4 for female patients
Other bloodwork may be indicated on the prescription, including: WBC, ANC, platelets, etc. If the
relevant recommendations on dosing adjustments are included you can use that information as a general guide to gain a better understanding of the patient’s situation, and appreciate if the patient is in the risk range. That information can also be helpful in cases when the dose is being reduced as it will provide you with the reason for that dose reduction.
Sometimes the prescriber may choose to override the guidelines recommendations therefore, if you see